A probe by New York State’s top financial services cop into possible fraud in the sale of pricey mortgage insurance is being stonewalled by a pair of Wall Street firms who refuse to turn over data, The Post has learned.

Ben Lawsky, the Superintendent of the state’s new Department of Financial Services, was rebuffed by Citigroup’s mortgage unit, Citimortgage, and insurance agent Assurant Inc. — both of which are maintaining that they don’t have to comply with the state requests, according to sources familiar with the situation.

Lawsky subpoenaed the two companies in an attempt to get information about their policies of assigning the costly mortgage insurance on certain home loans.

The so-called forced-insurance practices has become a major cause celebre for Lawsky, who issued more than 30 subpoenas to a number of insurance agents and mortgage subsidiaries of JPMorgan Chase, Morgan Stanley and Wells Fargo as far back as October.

At this point, Citigroup is claiming that the DFS does not have the authority to subpoena certain information from Citimortgage prior to the passage of Dodd-Frank, which went into effect on July 21.

“As Citimortage well knows, we are conducting a large-scale, intensive investigation into all aspects of the forced placed insurance industry. Citimortgage should immediately cooperate and desist in any efforts to thwart the scope of our investigation,” Lawsky said in a letter to Citi today, a copy of which was obtained by The Post.

In a letter to Assurant officials, Lawsky’s office accuses the insurance agent of destroying e-mails, despite receiving an Oct, 3 subpoena for documents.

Since being confirmed in May as the head of the newly-minted DFS, Lawksy has publicly announced that he is probing whether banks steered homeowners into such pricey insurance policies in exchange for kickbacks.

“Assurant respectfully disagrees with the New York Department of Financial Services position regarding the Company’s document retention practices,” said an Assurant spokesman. “In an effort to address the Department’s concerns, however, while this matter is pending, we are modifying our records retention practices.”

“We were very surprised by today’s letter. During ongoing, good-faith discussions with the New York Department of Financial Services, including as recently as today, we have indicated that we intend to respond to the subpoena voluntarily,” Citigroup said in a statement.

“We have not filed any objection or response to the subpoena, and in fact, a response is not yet due. As to issues concerning lender-placed insurance, we believe that it is responsible for lenders to protect their interests in properties that secure loans, and that we have acted in compliance with all applicable laws.”

A spokesman for Lawsky’s office declined to comment.

During the mortgage crisis, forced-placed insurance became a hot industry as more and more homeowners were forced to pay high premiums imbedded in their mortgage payments originated by banks even as the housing market crashed and their houses plummeted in value.